Add stub code for IFMA intrinsics in Rust.

Cargo.toml

@@ -72,6 +72,7 @@ u64_backend = []
 # The AVX2 backend uses u32x8s with u64x4 products.
 # It uses the u64 code for serial operations.
 avx2_backend = ["nightly", "u64_backend", "packed_simd"]
+ifma_backend = ["nightly", "u64_backend", "packed_simd", "yolocrypto"]
 
 # Signals that we're in the main build stage.  This is off by default,
 # to signal stage 1 of the build, where build.rs loads the library

build.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(feature = "ifma_backend", feature(simd_ffi))]
+#![cfg_attr(feature = "ifma_backend", feature(link_llvm_intrinsics))]
 #![cfg_attr(all(feature = "alloc", not(feature = "std")), feature(alloc))]
 #![cfg_attr(feature = "nightly", feature(cfg_target_feature))]
 #![allow(unused_variables)]
@@ -13,7 +15,7 @@ extern crate digest;
 extern crate rand;
 extern crate subtle;
 
-#[cfg(all(feature = "nightly", feature = "avx2_backend"))]
+#[cfg(all(feature = "nightly", any(feature = "avx2_backend", feature = "ifma_backend")))]
 extern crate packed_simd;
 
 use std::env;

src/backend/mod.rs

@@ -21,7 +21,11 @@
 //! `32bit` since identifiers can't start with letters, and the backends
 //! do use `u32`/`u64`, so this seems like a least-bad option.
 
-#[cfg(not(any(feature = "u32_backend", feature = "u64_backend", feature = "avx2_backend")))]
+#[cfg(not(any(
+    feature = "u32_backend",
+    feature = "u64_backend",
+    feature = "avx2_backend"
+)))]
 compile_error!(
     "no curve25519-dalek backend cargo feature enabled! \
      please enable one of: u32_backend, u64_backend, avx2_backend"
@@ -29,5 +33,8 @@ compile_error!(
 
 pub mod serial;
 
-#[cfg(all(feature = "avx2_backend", target_feature = "avx2"))]
+#[cfg(any(
+    all(feature = "ifma_backend", target_feature = "avx512ifma"),
+    all(feature = "avx2_backend", target_feature = "avx2"),
+))]
 pub mod vector;

src/backend/vector/ifma/field.rs

@@ -0,0 +1,40 @@
+// -*- mode: rust; coding: utf-8; -*-
+//
+// This file is part of curve25519-dalek.
+// Copyright (c) 2018 Henry de Valence
+// See LICENSE for licensing information.
+//
+// Authors:
+// - Henry de Valence <hdevalence@hdevalence.ca>
+
+use core::ops::{Add, Mul, Neg};
+use packed_simd::{i32x8, u32x8, u64x4, IntoBits};
+
+use backend::serial::u64::field::FieldElement51;
+
+#[allow(improper_ctypes)]
+extern "C" {
+    #[link_name = "llvm.x86.avx512.vpmadd52l.uq.256"]
+    fn madd52lo(z: u64x4, x: u64x4, y: u64x4) -> u64x4;
+    #[link_name = "llvm.x86.avx512.vpmadd52h.uq.256"]
+    fn madd52hi(z: u64x4, x: u64x4, y: u64x4) -> u64x4;
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn vpmadd52luq() {
+        let x = u64x4::splat(2);
+        let y = u64x4::splat(3);
+        let mut z = u64x4::splat(5);
+
+        z = unsafe { madd52lo(z, x, y) };
+
+        assert_eq!(z, u64x4::splat(5 + 2*3));
+    }
+
+}
+
+

src/backend/vector/ifma/mod.rs

@@ -0,0 +1,11 @@
+// -*- mode: rust; -*-
+//
+// This file is part of curve25519-dalek.
+// Copyright (c) 2018 Henry de Valence
+// See LICENSE for licensing information.
+//
+// Authors:
+// - Henry de Valence <hdevalence@hdevalence.ca>
+
+pub(crate) mod field;
+

src/backend/vector/mod.rs

@@ -28,5 +28,8 @@ pub(crate) use self::avx2::{
     constants::BASEPOINT_ODD_LOOKUP_TABLE, edwards::CachedPoint, edwards::ExtendedPoint,
 };
 
+#[cfg(all(feature = "ifma_backend", target_feature = "avx512ifma"))]
+pub mod ifma;
+
 pub mod scalar_mul;
 

src/lib.rs

@@ -10,6 +10,9 @@
 
 #![no_std]
 
+#![cfg_attr(feature = "ifma_backend", feature(simd_ffi))]
+#![cfg_attr(feature = "ifma_backend", feature(link_llvm_intrinsics))]
+
 #![cfg_attr(all(feature = "alloc", not(feature = "std")), feature(alloc))]
 #![cfg_attr(feature = "nightly", feature(cfg_target_feature))]
 #![cfg_attr(feature = "nightly", feature(external_doc))]
@@ -38,7 +41,7 @@ extern crate alloc;
 #[macro_use]
 extern crate std;
 
-#[cfg(all(feature = "nightly", feature = "avx2_backend"))]
+#[cfg(all(feature = "nightly", any(feature = "avx2_backend", feature = "ifma_backend")))]
 extern crate packed_simd;
 
 extern crate rand;